.TH std::experimental::future::then 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::experimental::future::then \- std::experimental::future::then

.SH Synopsis
   template< class F >
   future</* see below */> then( F&& func ) ;

   Attach the continuation func to *this. The behavior is undefined if *this has no
   associated shared state (i.e., valid() == false).

   Creates a shared state associated with the future object to be returned, and a copy
   fd of func constructed as if by DECAY_COPY(std::forward<F>(func)) evaluated in the
   thread calling then, where DECAY_COPY is defined as

   template<class T>
   std::decay_t<T> DECAY_COPY(T&& v)
   {
       return std::forward<T>(v);
   }

   When the shared state currently associated with *this is ready, the continuation
   INVOKE(std::move(fd), std::move(*this)) is called on an unspecified thread of
   execution, where INVOKE is the operation defined in Callable. If that expression is
   invalid, the behavior is undefined.

   Any value returned from the continuation is stored as the result in the shared state
   of the returned future object. Any exception propagated from the execution of the
   continuation is stored as the exceptional result in the shared state of the returned
   future object.

   Let U be the return type of the continuation (i.e.
   std::result_of_t<std::decay_t<F>(std::experimental::future<T>)>). If U is
   std::experimental::future<T2> for some type T2, then the return type of then is
   std::experimental::future<T2>, otherwise it is std::experimental::future<U>. This is
   known as implicit unwrapping.

   If implicit unwrapping takes place and the continuation returns an invalid future,
   then the shared state is made ready with an exception of type std::future_error with
   an error condition of std::future_errc::broken_promise.

   After this function returns, valid() is false.

.SH Parameters

   func - a continuation to be attached

.SH Return value

   A std::experimental::future object associated with the shared state created by this
   object. valid() == true for the returned object.

.SH Example

    This section is incomplete
    Reason: no example

.SH Category:
     * Todo no example
